The radiography image of chest is the key technology of diagnosis for the pulmonary disease. X-ray imaging is the main measures to the medical screening of pulmonary diseases such as the pulmonary inflammation, lump, tuberculosis, lung cancer and so on; Along with the development of digital imaging technology, the digital radiography i.e. DR (Digital Radiography) gradually replaces the traditional chest perspective imaging method; DR refers to a new technology of directly conducting digital X-ray photography under the control of computers, which means to convert the X-ray information which penetrates the human body into the digital signal by adopting amorphous silicon flat-panel detectors, rebuild the image through the computer and conduct a series of image post-processing; The DR system is mainly composed of several parts such as the X-ray generation device, direct conversion flat panel detector, system controller, image monitor, image treatment working station and so on; As the DR technical dynamic range is wide and the X-ray light quantum detection efficiency (DQE) is high, it has quite a large latitude in exposure. Even though the condition of exposure is slightly bad, the excellent images can be obtained; DR imaging has high sharpness and low radiation, which has become the mainstream technical device in a lot of hospitals and the grassroots physical examination centers in our country.
In our country, the general purpose of shooting chest DR image is to conduct the screening of the serious and infectious diseases such as tuberculosis or lung cancer and etc; The tuberculosis is caused by the mycobacterium tuberculosis, which is easily spread through spray in the air and even the aerosol; The majority of tuberculosis patients is young adults, which will result in the labor loss for the families and the society; The world health organization indicates that the tuberculosis is the important public health problem all over the world. In our country, there are approximately 5000000 active pulmonary tuberculosis patients at present and there are 5*104 people die of tuberculosis every year; The tuberculosis is one of the main infectious disease which is importantly prevented and controlled in our country; In consideration of the fact that the damage of the tuberculosis is serious and the difficulty of the prevention and control work is big while the scale of local tuberculosis prevention and control teams at different levels is still small, whose power and expenditure cannot adapt the prevention and control demand, the technology and capital input shall be strengthened and the medical prevention combination mechanism shall be established to form the practical and effective prevention and treatment system; At present, two weak and difficult links of early-stage notice and treatment management exist in the implementation of the prevention and treatment for the tuberculosis; Under such circumstance, the screening program for the tuberculosis patients among the focus groups is gradually launched inside the country by using the essential public health service; Being compared with the tuberculosis, the severity degree of damage to the lung cancer on the health of the patients is higher than that of the former; It is universally acknowledged that the death rate of lung cancer is considerably higher than that of other cancers and it increases by years in recent years; The imageological examination is one of the important technical measures in the aspects of diagnosis, test, prevention and treatment on the cancer; The generally major research object of chest imaging is the lung cancer, which normally observes the corresponding lung images through establishing the lung window; Lung cancer is a neoplastic disease which is related to the smoking, atmospheric pollution and low immunologic function; For example, the repeated inflammatory stimulation of factors like the dust-haze in recent years will bring the chronic damage, affecting the normal epithelial function of the bronchial epithelium and the immune antiviral state of the body and having facilitation affect on the occurrence of lung cancer.
The principle of DR radiography imaging is that the human tissue has difference of density and thickness. When the X-ray penetrates different tissues of the human body, the absorption degrees of X-ray vary. Thus, the quantity of X-ray that reaches the screen varies and form the images with different grayscale intensity; It uses the imaging differences of different density to the human tissue under the X-ray to analyze the thickness and density difference of the tissues, speculates and evaluates the possible diseased region therein to offer basis for the diagnosis for the doctors; However, the structure of human tissue is complicated. The thoracic cavity and enterocoelia include the key organs of the human body, which include all kinds of visceral organs with high density and low density; Therefore, the images of all organs and tissues overlap with each other, which has quite a large influence on the observation and judgment; So the reading and judgment of the DR radiography have very high requirement on the experience and vigor of the doctors, in which the early stage and atypical cases are easy to be ignored. Although the DR radiography examinations of certain size are conducted in the primary hospitals and medical examination points, the DR radiography examinations of extra large scale are very hard to be truly launched with the current existing labor and technical resources.
Although the reading and diagnosis of DR radiography has large difficulty, the digital technology adopted by it offers the basic technical conditions for the post-treatment to the targeted images in accordance with the clinical demand; The image post-treatment is the largest characteristic of digital images; The targeted treatment can be conducted on the images in accordance with the diagnosis demand through developing algorithm and software function only if the original data is reserved, which improves the diagnostic rate; Under the current technical conditions, the targeted DR radiography image treatment and analysis still have difficulty; The existing devices can only realize the functions in generic form of the DR radiography such as enhancing the sharpness of edges, magnifying the roaming, image stitching, adjustment of window width and window level in region of interest, etc. or the measurement of the basic distance, area and density; The difficult realization of the atopic functions aiming at the specific organs or lesions type is resulted from the fact that the image treatment technology aiming at the tasks and objects still have a lot of technical difficulty in the application layer; As far as the chest DR radiography, one major difficulty point of the intelligent interpretation to the digital images is how to determine the area of lung lobe; If the scope of lung lobe can be accurately confirmed and the interference outside the lung can be weakened or eliminated, it will be more beneficial for the notice of slight lesion; In addition, the shape of the lung lobe contour itself also is the important factor of judging relevant physiological index of the people receiving physical examination; Reliable lung lobe contour extraction algorithm can reduce the time of rechecking for the people receiving physical examination and reduce the number of chest images, letting theirs obtain the definite diagnosis on their nidus from the doctors at the cost of lower radiation dosage; At present, there is no lung lobe contour extraction method that aims to the treatment of DR radiography.